1. Technical Field
The present invention relates to a method for designing a progressive-power lens used in specific work, a progressive-power lens designing system, and a progressive-power lens.
2. Related Art
A progressive-power lens typically includes a near region corresponding to near vision, a far region disposed above the near region and corresponding to far vision, a progressive region which is disposed between the far and near regions and where the power continuously changes, and intermediate side regions provided on both sides of the progressive region.
The near region, the far region, and the progressive region are distinct vision regions through which target objects are distinctly viewed, whereas the intermediate side regions located on both sides of the progressive region are not used to distinctly view the target objects. Therefore, when a spectacle wearer moves the line of sight into any of the intermediate side regions, the wearer senses blurring due to astigmatism or a dioptric power error.
There has been a proposed progressive-power spectacle lens suitable for car driving, a lens suitable for personal computer operation, and lenses dedicated to other applications. A spectacle lens of this type is so designed that the sizes of the far and near regions, the length of a progressive corridor, and aspheric coefficients are appropriately adjusted.
To increase the width of the field of view perceived by the spectacle wearer, there is a spectacle lens designed by determining a deviation of a saggital plane of the spectacle wearer from a standard saggital plane, selecting an optimization target as the function of the deviation, and performing optimization based on the target (JP-T-2008-511033).
There is also a known method for designing a progressive-power lens suitable for a specific application by setting the distances to objects in a far field and a near field and the ability of accommodation for the objects (see JP-T-2005-500585).
There is another known method for providing a progressive-power lens suitable for the wearer in a specific application by checking how a lens fits the wearer based on a scene object image appropriately representing the intended use of the lens and selecting an optimum lens (see JP-A-2008-39997).
In a progressive-power lens of related art, in which the far and near regions are used to distinctly view a target object, when a spectacle wearer moves the line of sight from these regions to any of the intermediate side regions located to the right and left thereof, the spectacle wearer suffers from blurring due to astigmatism or a dioptric power error. For example, a spectacle wearer who is driving a car uses the far region when directing the line of sight toward a car running in front of the car driven by the wearer, a traffic light, or any other object, whereas using the near region when directing the line of sight toward an on-vehicle indicator immediately in front of the wearer. On the other hand, when the wearer moves the line of sight toward a side-view mirror provided on a side of the car, the wearer suffers from blurring because the line of sight passes through the corresponding intermediate side region. To avoid the blurring, the wearer needs to turn his or her head rightward or leftward toward the side-view mirror.
There is a progressive-power lens optimized for car driving by adjusting the sizes of the near and far regions and aspheric coefficients. Using the lens, however, still cannot sufficiently enlarge a distinct vision area and the wearer suffers from blurring when moving the line of sight into any of the intermediate side regions, resulting in difficulty distinctly viewing an object.
The related art described in JP-T-2008-511033 only considers the dominant eye but does not enlarge the distinct vision area for a specific application. That is, when the wearer does not turn his or her head but moves the line of sight, the wearer suffers from blurring, as in the case of the progressive-power lens of related art described above.
The progressive-power lenses described in JP-T-2005-500585 and JP-A-2008-39997 similarly cause the wearer to suffer from blurring when the wearer does not turn his or her head but moves the line of sight.
The problem with the spectacle lens described above occurs not only in car driving but also in personal computer operation and other applications.